In recent years, streetcars and the like have adopted a low floor vehicle design in which a floor surface in the vehicle is set close to a road surface to reduce a difference in level of stepping up and stepping down for passengers so as to make the vehicles barrier-free. In such a streetcar, because of limitations such as road traffic conditions, a large number of curved tracks curving at a curvature radius equal to or less than 20 m, are provided. There is a problem in that, when the vehicle enters a curved track, an angle in a traveling direction of wheels with respect to a tangential direction of the curved track (hereinafter referred to as “attack angle”) increases. When this attack angle is large, in wheels present on an outside rail during traveling on the curved track, in some cases, flanges of the wheels come into contact with the track. At this point, pressure is applied from the wheel flanges to the vehicle, the lateral pressure of the vehicle increases, and vibration and creaking sounds occur in the vehicle. As a result, there is a problem in that riding comfort of passengers is degraded and the wheel flanges wear out.
While taking such a problem into account, a low floor vehicle called an LRV (Light Rail Vehicle) as disclosed in Patent Literature 1, has been developed. In FIG. 13, an example of the configuration of this LRV is shown. A traveling direction of this LRV is indicated by an arrow A. In the explanation, it is assumed that the traveling direction is a vehicle front. Referring to FIG. 13, the LRV includes two front vehicles 102 and one intermediate vehicle 103 traveling on a track 101. As a vehicle composition, the one intermediate vehicle 103 is arranged between the two front vehicles 102.
Pin connectors 105 are arranged along an axis which extends in a vehicle vertical direction in connecting sections 104 between the front vehicles 102 and the intermediate vehicle 103. The front vehicles 102 are coupled to the intermediate vehicle 103 to be capable of turning around the pin connectors 105. Therefore, the front vehicles 102 and the intermediate vehicle 103 can curve around the pin connectors 105 so as to correspond to a curvature radius R of the curved track 101. Furthermore, in the connecting sections 104, any of dampers, springs, and the like (not shown) may be provided to suppress the turning of the front vehicles 102 and to secure safety during high speed traveling of the vehicle.
Trucks 107 are arranged under vehicle bodies 106 of the front vehicles 102. As shown in FIGS. 14 to 16, a pair of left and right wheels 108 is provided on each of a vehicle front side and a vehicle rear side of the truck 107. The pair of wheels 108 is configured to be pivotable independently from each other around the same axis 108a which extends in a vehicle width direction, and is coupled by a journal member 109. The journal member 109 is arranged on each of a vehicle front side and a vehicle rear side of each of truck frames 110. The truck frames are formed as frame members of the truck 107. A conical rubber 111 is provided as a shaft spring for the wheel 108 between the journal member 109 and the truck frame 110. Vibration transmitted from the wheel 108 to the truck frame 110, is suppressed by this conical rubber 111. Furthermore, the journal member 109 extends in a position close to the road surface between the pair of wheels 108. A floor surface (not shown) in the vehicle is arranged on the journal member 109. Therefore, the floor surface in the vehicle is configured to be close to the road surface.
Referring to FIG. 13 again, when the vehicle traveling in the traveling direction enters the curved track 101, force directed in a straight forward direction by inertia, acts on the vehicle bodies 106. Force directed in a tangential direction of the curved track, acts on the trucks 107. Therefore, force acting on the entire front vehicles 102 is unbalanced. At this point, the straight forward force by inertia also affects the trucks 107. The trucks 107 are less easily curved along the curved track 101. As a result, an attack angle α, which is an angle in the traveling direction (indicated by an arrow C) of the wheel 108 with respect to the tangential direction (indicated by an arrow B) of the curved track, increases. It is likely that wheel flanges 108b (shown in FIGS. 14 to 16) of the wheels 108 on an outside rail side come into contact with the track. At the time of this contact, pressure is applied from the wheel flanges 108b to the vehicle, lateral pressure of the vehicle increases, and vibration and creaking sound occur in the vehicle. As a result, there is a problem in that riding comfortableness of passengers is degraded and the wheel flanges 108b wear out.
To absorb such unbalance of force, the trucks 107 are configured to be movable in the vehicle width direction with respect to the vehicle bodies 106. Specifically, as shown in FIGS. 14 to 16, traction rods 112 which transmit traction force of the truck 107 to the vehicle body 106, are arranged along a vehicle longitudinal direction. Ends 112a on the vehicle rear side of the traction rods 112 are attached to the truck 107 side via a spherical bush or a rubber vibration insulator (not shown). Ends 112b on the vehicle front side of the traction rods 112 are attached to the vehicle body 106 side via a spherical bush or a rubber vibration insulator (not shown).